Multivibrator system for logic circuits



United States Patent 3,234,402 MULTEVIBRATOR SYSTEM FOR LOGIC CIRCUITS Lucien Budts, Francois de Senigon de Roumefort, and

Jeanne Ealigant (Wife of De Senigon tie Ronmefort), Paris, France, assignors to Societe de Diffusion dEquipernents Electroniques S.D.E.E., Paris, France, a corporation Filed Mar. 27, 1962, Ser. No. 182,896 Claims priority, application France, Mar. 30, 1961,

857,337, Patent 79,516 7 Claims. (Cl. 307-885) The present invention relates to transistorized multivibrator systems of the type disclosed in our earlier patent application Ser. No. 829,699, filed on July 27, 1959, now Patent No. 3,041,477.

The object of the present invention, is to provide further improvements in that system.

These improvements consist essentially in adding to the circuit shown in this patent: suitably disposed diodes and a common connection point for all the functional units of a complex circuit, the modification thus facilitating the use of the units while improving their stability.

These improvements will be more readily understood from the accompanying drawing, in which:

FIG. 1 is a diagram of an improved functional unit, according to the invention; and

FIG. 2 is a diagram of a control unit operating upon the receipt of an instruction or by self-feed.

The functional unit of FIG. 1 is a transistor flip-flop or multivibrator. sistor T1 and T2, respectively. One is cut off when the other is conductive.

The control point is denoted by reference numeral 7. If there is no signal at this point, the transistor T1 conducts and the multivibrator is regarded as being in its inoperative state; at that time the potential of point 1 (i.e. of the collector of transistor T1) is approximately equal to that of the point 9 and the point 15 (i.e. the collector of transistor T2) is at a potential of about 24 volts which diflers considerably from that of the point 9 tied to the emitters of the two transistors.

If a signal appears at the point 7, a positive potential being applied thereto, the multivibrator is considered as operative (with transistor T2 conducting) and the point 1 passes to a voltage of -24 volts, the point 15 assuming a potential close to that of the point 9.

The system is energized by a source of direct current connected to the junction 5, maintained at a negative potential here given as 24 volts, and the point 10 tied to the positive terminal of the source.

The point 9 represents a common terminal of several functional units of the type illustrated in FIG. 1.

Such a unit has the following properties:

When voltage is applied across the DC. terminals 5, 10, and in the absence of any control signal on terminal 7, the multivibrator will pass into its inoperative state, the transistor T2 being deactivated while the transistor T1 becomes conductive.

The base of T2 is connected to a junction formed by resisters R2, R7 and R9. This latter resistor is in parallel with the resistor R10 at a beginning of the application of voltage, while C is not charged.

The base of T1 is connected to potentiometer bridge formed by the resistors R4 on the one hand, R8 and R6 on the other hand, in parallel with resistive branch R11 through the rectifier means or diode D2.

It follows from the foregoing that the base of transistor T2 is positive and T2 is cut off. There is no current flow through the resistor R3 and the output point 15 is at a voltage in the region of 24 volts.

The base of T1 is negative and hence T1 conducts the It comprises a first and a second tran- Patented Feb. 8, 1966 emitter-collector current being limited by the resistors R1 and R2. The potential between the points 9 and 1 is at a minimum.

The operation of the system is as if the points 9 and 1 were in closed contact, representing an inoperative condition. The potential between the points 9 and 15 being as high as possible, it may be said that the contact is open between points 9 and 15, representing the operative condition.

The passage of the functional unit into the operative condition is abrupt and may be produced by a control signal which may be either continuous or variable with time.

In the first case, the point 7 is connected to the positive pole, the contacts I2 being closed. The transistor T1 is thus cut off and the point 1 becomes more negative.

The base of T2 therefore goes negative and T2 becomes conductive.

The potential across the junctions or terminals 9 and 15 is practically zero (closed operative contact). The purpose of the capacitor C6 is to hold constant the potential of the terminal 9 during the flip-flop operation. This capacitor is a single capacitor common to all the units of an installation, and its value is about 10 microfarads per functional unit used.

In the second case, a variable current is applied to the point 7, for example by disposing a continually decreasing resistance X between the positive terminal of the source and the point 7. The current passing through the base of T1 will therefore drop, the emitter-collector current of T1 will fall and the junction 1 will become more negative; the same applies to the bridge (R7/R9).

For a certain value of this variation, the base of T2 becomes negative and T2 begins to conduct. The diode D1 tends to accelerate this process by reducing the bias of T1 through R3.

This flip-flop process is abrupt and takes place in a few microseconds.

Similarly, the passage of the unit into the inoperative condition is abrupt and may be produced by a control signal which is constant or which is variable with time.

In the former case, any signal disappears at the point 7 (for example by the opening of a switch), the base of transistor T1 is then biased negatively via resistors R11 and D2. The transistor T1 conducts and the potential at the point 1 becomes less negative so as to cut off transistor T2.

There is thus closed inoperative contact between the points 1 and 9 of neighboring potential.

There is a considerable potential difference between the points 9 and 15 and the open operative contac is created.

Alternately, a variable voltage is applied to the terminal 7, for example by connecting a continually increasing resistance X between the positive supply terminal and the point 7. The same process as described above takes place.

Finally, the functional unit may be self-energizing.

It will be assumed that a signal applied to the point 7 has brought the functional unit into the operative position.

If this signal disappears and if it is desired to prevent the unit from returning to the inoperative state, the base of transistor T1 must be prevented from becoming negative through the resistor R11. To this end, it is only necessary to apply a positive voltage to the point 8, either by connecting said terminal directly to the positive supply terminal with the switch I, or through a suitable resistance Y.

As long as the potential of the point 8 does not vary, the diode D2 acts as a valve and the circuit remains in sary to cancel the order produced at the .point 8.

- of the same sign.

.tionsused at the point 7 by the control units. can be digards number.

the operative condition, the passage into this condition naturally having been produced by a signal at the point 7. To obtain self-feeding or self-energization, it is possible to make the point 8 positive before or after the operative order or instruction has been applied, the circuit of the diode (D2, R11) acting only 'for the return to the prior condition.

In practice, the functional units are designed according to the circuit diagram shown in FIG. 1. It will be seen that the point 1 'is connected to three diodes and the point 15 to another three diodes. Thisarrangement gives three inoperative and three operative states, the common junction being the point '9. Each functional unit ,is in the form of a unit having plug-in rectangular surfaces. The plug contains the connections indicated by reference numerals 1 to 15 inFlG. l.

Referring now more particularly to the improvements forming the subject of the present invention, the diode DI, the ,diode D2 and the point will be considered .R6 and .R8 is so designed that when the three output points 12, 13, 14, are connected to control units the potentialof R3 .is equal to the potential of R6. Asa result,

the diode D1 is at the minimum cut-off level and the .current at the base oftransistor T1 will remain constant for a .zero load on theoutput points considered or for .the maximum load provided. The current required to cancelout the bias of transistor T1 will always be constant and will be more readily controllable by an external element. In other 'words, the flip-flop will always be controlled by.the point 7 inresponse to currents of constant characteristics.

II.-Dide D2 In the systems according to the above-mentioned patent, only the resistor R11 was connected to various flip-flops. The .result .of this was a limitation of the number of possible flip-flops and the impossibility of planning selffeedingprograms comprising a limitednumber of AND functions and a limited number of OR functions and hence theimpossibility of enabling the conventional possibilities of electromagnetic relays to be embodied-simply.

The. fact that the point 8 .(FIG. 1 ),is broughtto a positive potential with respect to the point 9 bringsthediode .D2 into thecut-off position. As; a result,.ifthe functional unit is rendered operative'byway of the point '7, the disappearance ofthisinstruction will not result in the return oftthis .unit to theinoperative state. In fact, @it is'only the resistor R11 which produces this effect and because -D2 .is cut-ofl? the basetransistor T1 does .notreceive the .bias current required to return the flip-flop into its prior condition. To obtain this returnto O, it will be neces- It should be noted that orders received at the points 7 and 8 foroperation v(point 7)or selfafeeding (point 8) are It follows that the logical combinarectly applied to the point 8 without any limitation as re- When-the functional unit .is in the inoperative. state, thefactthat the .point 8 is rendered positive with respect .to thetpoint 9 does ,not'affect thepositionofv the flip-flop. In fact, transistor .T1 remains biased by.the resistors R8 and R6. The same operational resultsare therefore obtained asin the case of electromagnetic relays, in which. operation ofthe relay is not produced when the latter is brought to the self-feeding state, although the relay is held operative when this condition 'hasbeenproduced by other means.

IIL-Common point 9 In an assembly of functional units connected together to provide a predetermined program, it should be noted that these output points 12, 13, 14 and 2, 3, 4 (FIG. 1) are at a potential in the region of the point 9 when the points in question correspond to conduction of transistor T1 and T2. As a result, the point 9 will be common to all the functional units so that irrespective of the possible variations of the resistances of the circuits, all the emitters of the transistors are at the-same potential. The transmission of orders at a given level therefore enables a stable system to be obtained.

Like the foregoing, the flip-flop shown in FIG. 1 will be in the operative position when the point 7 is made positive with respect to the point 9, either by direct connection to the position pole or by the use of a calibrated resistance between the point 7 and the positive pole, or by the use of a control unit, the output points 25 of which (FIG. 2) is connected to the point 7 ('FIG. 1),

and the input point 30 (FIG. 2) -is connected toianother functional unit. This functional unit will control the next. It should be remembered that the use of these control units combines any number'of functional units and, in certain conditions, enables all logical programs used in magnetic relay iautomatiosystems to be embodied, i.e. AND or QR functions, or AND and OR functions, the object always being to :replace electromagnetic relays by transistorised flip-flops :according ;to the invention.

What we claim is:

1. A multivibrator circuit arrangement comprising a first and a second transistor each with a base electrode, an emitter electrode, a collector electrode, a first resistive branch connecting the base electrode of one .of'said transistors to a source of emitterpotential, a second resistive branch connecting said base electrodeofsaid one of said transistors to the collector electrode of the otherof said transistors and forming with said first-branch apotentiometer, and resistance means connectingsaid collector electrode of said other of said transistor to a source of collector potential, the potentials of said sources and the branches ofeach potentiometer maintaining each of said transistors nonconductive upon the passage ,of current through the other transistor and the associated; resistance means; a common resistor connecting the emitter electrodes-of both transistors to said source of emitter potential; and input connected to the base electrode of said first transistor for controlling the potential thereof to maintain said first :transistorconductive in-the absence of a switching signal on .said input; at least'one output connected to the collector electrode of said second-transistor; rectifier means connected in said second-resistive branch with a polarity facilitating the flow of a-biasing current in the conductive condition of said second transistor formaintaining the base electrode of said first transistor at cutoff potential; and circuit means connecting said rectifier means to a source of biasing potential for isolating the base electrode of said'first transistor from said. output in the nonconductive condition of said second transistor.

2. A multivibrator circuit arrangement comprising a first and second transistor each with a base electrode, an emitter electrode, a collector electrode, a first resistive branch connecting the base electrode of one of said transistors to a source of emitter potential, asecond resistive branch connecting said base electrode of said one of said transistors to the collector electrode of theother of said transistors and forming with said first branch a potentiometer, and resistance means connecting. said collector electrode of said other of said transistorsto a source of collector potential, the potentials of said sources and the branches ofcach potentiometer maintaining each of said transistors nonconductive upon the passage of current through the other transistor and therassociated resistance means; a common resistor connecting the emitter electrodes of both transistors to said source of emitter potential; an input connected to the base electrode of said first transistor for controlling the potential thereof to maintain said first transistor conductive in the absence of a switching signal on said input; at least one output connected to one of said collector electrodes; a resistive connection extending from the base electrode of said first transistor to said source of collector potential; circuit means having a junction with said connection for connecting said connection to a source of blocking potential for the base electrode of said first transistor; and rectifier means in said connection between said junction and the base electrode of said first transistor with a polarity preventing the application of said blocking potential to the base electrode of said first transistor in the absence of a biasing current through said rectifier means due to conduction of said second transistor.

3. A multivibrator circuit arrangement comprising a first and a second transistor each With a base electrode, an emitter electrode, a collector electrode, a first resistive branch connecting said base electrode of one of said transistors to a source of emitter potential, a second resistive branch connecting said base electrode of said one of said transistors to the collector electrode of the other of said transistors and forming with said first branch a 130- tentiometer, and resistance means connecting said collector electrode of said other of said transistors to a source of collector potential, the potentials of said sources and the branches of each potentiometer maintaining each of said transistors nonconductive upon the passage of current through the other transistor and the associated resistance means; a common resistor connecting the emitter electrodes of both transistors to said source of emitter potential; an input connected to the base electrode of said first transistor for controlling the potential thereof to maintain said first transistor conductive in the absence of a switching signal on said input; at least one output connected to the collector electrode of said second transistor; a first diode connected in said second resistive branch with a polarity facilitating the fiow of a biasing current in the conductive condition of said second transistor for maintaining the base electrode of said first transistor at cutoff potential; first circuit means connecting said first diode to a source of biasing potential for isolating the base electrode of said first transistor from said output in the nonconductive condition of said second transistor; a resistive connection extending from the base electrode of said first transistor to said source of collector potential; second circuit means having a junction with said connection for selectively connecting said connection to a source of blocking potential for said base electrode of said first transistor; and a second diode in said connection between said junction and said base electrode of said first transistor with a polarity preventing the application of said blocking potential to the base electrode of said first transistor in the absence of said biasing current.

4. A multivibrator circuit arrangement comprising a first and a second transistor each with a base electrode, an emitter electrode, a collector electrode, a first resistive branch connecting said base electrode of one of said transistors to a source of emitter potential, a second resistive branch connecting said base electrode of said one of said transistors to the collector electrode of the other of said transistors and forming with said first branch a potentiometer, and resistance means connecting said collector electrode of said other of said transistors to a source of collector potential, the potential of said sources and the branches of each potentiometer maintaining each of said transistors nonconductive upon the passage of current through the other transistor and the associated resistance means; a common resistor connecting the emitter electrodes of both transistors to said source of emitter potential; capacitive means connected across said first resistive branch of said second transistor for rendering said first transistor preferentially conductive upon application of said emitter and collector potentials; an input connected to the base electrode of said first transistor for controlling the potential thereof to render. said first transistor nonconductive in the presence of a switching signal on said input; at least one output connected to the collector electrode of said second transistor; rectifier means connected in said second resistive branch with a polarity facilitating the fiow of a biasing current in the conductive condition of said second transistor for maintaining the base electrode of said first transistor at cutoff potential; and circuit means connecting said rectifier means to a source of biasing potential for isolating the base electrode of said first transistor from said output in the nonconductive condition of said second transistor.

5. A multivibrator circuit arrangement comprising a first and a second transistor each with a base electrode, an emitter electrode, a collector electrode, a first resistive branch connecting said base electrode of one of said transistors to a source of emitter potential, a second resistive branch connecting said base electrode of said one of said transistors to the collector electrode of the other of said transistors and forming with said first branch a potentiometer, and resistance means connecting said collector electrode of said other of said transistors to a source of collector potential, the potentials of said sources and the branches of each potentiometer maintaining each of said transistors nonconductive upon the passage of current through the other transistor and the associated resistance means; a common resistor connecting the emitter electrodes of both transistors to said source of emitter potential; capacitive means connected across said first resistive branch of said second transistor for rendering said first transistor preferentially conductive upon application of said emitter and collector potentials; an input connected to the base electrode of said first transistor for controllin the potential thereof to render said first transistor nonconductive in the presence of a switching signal on said input; at least one output connected to one of said collector electrodes; a resistive connection extending from the base electrode of said first transistor to said source of collector potential; circuit means forming a junction with said connection for connecting said connection to a source of blocking potential for the base electrode of said first transistor; and rectifier means in said connection between said junction and said base electrode of said first transistor with a polarity preventing the application of said blocking potential to the latter electrode in the absence of a biasing current through said rectifier means due to conduction of said second transistor.

6. A multivibrator circuit arrangement comprising a first and a second transistor each with a base electrode, an emitter electrode, a collector electrode, a first resistive branch connecting said base electrode of one of said transistors to a source of emitter potential, a second resistive branch connecting said base electrode of said one of said transistors to the collector electrode of the other of said transistors and forming with said first branch a potentiometer, and resistance means connecting said collector electrode of said other of said transistors to a source of collector potential, the potentials of said sources and the branches of each potentiometer maintaining each of said transistors nonconductive upon the passage of current through the other transistor and the associated resistance means; a common resistor connecting the emitter electrodes of both transistors to said source of emitter potential; capacitive means connected across said first resistive branch of said second transistor for rendering said first transistor preferentially conductive upon application of said emitter and collector potentials; an input connected to the base electrode of said first transistor for controlling the potential thereof to render said first transistor nonconductive in the presence of a switching signal on said input; at least one output connected to the collector electrode of said second transistor; a first diode connected in said second resistive branch with a polarity facilitating the flow of a biasing current in the conductive condition of said second transistor for maintaining the base electrode of said first transistor at cutoff potential; first circuit means connecting said first diode to a source of biasing potential for isolating the base electrode of said first transistor from said output in the noncondnctive condition of said second transistor; a resistive connection extending from the base electrode of said first transistor to said source of collector potential; second circuit means having a junction with said connection for connecting said connection to a source of blocking potential for said base electrode of said first transistor; and a second diode inserted in said connection between said junction and'said base electrode of said first transistor with a polarity preventing the application of said blocking potential to the latter electrode in the absence of said biasing current.

7 A circuit arrangement as defined in claim 6 wherein the common connection of said emitter electrodes has a junction connected to corresponding junctions of other transistor pairs forming part of additional multivibrator units, further comprising condenser means bridged across said common resistor for suppressing transient voltages (in said emitter electrodes. 7

References Cited by the Examiner UNITED STATES PATENTS 3,059,127 10/ 1962 Snijders 307-8815 ARTHUR GAUSS, Primary Examiner. 

1. A MULTIVIBRATOR CIRCUIT ARRANGEMENT COMPRISING A FIRST AND A SECOND TRANSISTOR EACH WITH A BASE ELECTRODE, AND EMITTER ELECTRODE, A COLLECTOR ELECTRODE, A FIRST RESISTIVE BRANCH CONNECTING THE BASE ELECTRODES OF ONE OF SAID TRANSSISTORS TO A SOURCE OF EMITTER POTENTIAL, A SECOND RESISTIVE BRANCH CONNECTING SAID BASE ELECTRODE OF SAID ONE OF SAID TRANSISTORS TO THE COLLECTOR ELECTRODE OF THE OTHER OF SAID TRANSISTORS AND FORMING WITH SAID FIRST BRANCH A POTENTIOMETER, AND RESISTANCE MEANS CONNECTING SAID COLLECTOR ELECTRODE OF SAID OTHER OF SAID TRANSISTOR TO A SOURCE OF COLLECTOR POTENTIAL, THE POTENTIALS OF SAID SOURCES AND THE BRANCHES OF EACH POTENTIOMETER MAINTAINING EACH OF SAID TRANSISTORS NONCONDUCTIVE UPON THE PASSAGE OF CURRENT THROUGH THE OTHER TRANSISTOR AND THE ASSOCIATED RESISTANCE MEANS; A COMMON RESISTOR CONNECTING THE EMITTER ELECTRODES OF BOTH TRANSISTORS TO SAID SOURCE OF EMITTER ELECTIAL; AND INPUT CONNECTED TO THE BASE ELECTRODE OF SAID FIRST TRANSISTOR FOR CONTROLLING THE POTENTIAL THEREOF TO MAINTAIN SAID FIRST TRANSISTOR CONDUCTIVE IN THE ABSENCE OF A SWITCHING SIGNAL ON SAID INPUT; AT LEAST ONE OUTPUT CONNECTED TO THE COLLECTOR ELECTRODE OF SAID SECOND TRANSISTOR; RECTIFIER MEANS CONNECTED IN SAID SECOND RESISTIVE BRANCH WITH A POLARITY FACILITATING THE FLOW OF A BIASING CURRENT IN THE CONDUCTIVE CONDITION OF SAID SECOND TRANSISTOR FOR MAINTAINING THE BASE ELECTRODE OF SAID FIRST TRANSISTOR AT CUTOFF POTENTIAL; AND CIRCUIT MEANS CONNECTING SAID RECTIFIER MEANS TO A SOURCE OF BIASING POTENTIAL FOR ISOLATING THE BASE ELECTRODE OF SAID FIRST TRANSISTOR FROM SAID OUTPUT IN THE NONCONDUCTIVE CONDITION OF SAID SECOND TRANSISTOR. 